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Year 2 haem mine > Disorders of haemostasis > Flashcards

Disorders of haemostasis Flashcards

1
Q

minor bleeding symptoms examples:

A 
easy bruising 
gum bleeding 
frequent nosebleeds 
bleeding after tooth extraction 
post operative bleeding
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2
Q

2 main causes of abnormal haemostasis and their sub causes

A

Lack of a specific factor

  • Failure of production: congenital and acquired
  • Increased consumption/clearance

Defective function of a specific factor

  • Genetic defect
  • Acquired defect – drugs, synthetic defect, inhibition
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3
Q

what are the disorders of primary haemostasis regarding?

A

platelets
VWF
vessel wall

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4
Q

what disorders can affect the platelets

what is low platelet count called and what can it be caused by?

A

*Low numbers: “thrombocytopenia”
Bone marrow failure eg: leukaemia, B12 deficiency
Accelerated clearance eg: immune (ITP), DIC.
pooling and destruction in an enlarged spleen

*impaired function: hereditary absence of glycoproteins or storage granules. Acquired due to drugs: aspirin, NSAIDs, clopidogrel

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5
Q

explain auto-ITP

A

there are antibodies that develop against the platelets and binding of these antibodies means that they are cleared rapidly by the macrophages
ITP is a very common cause of thrombocytopenia

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6
Q

mechanisms and causes of thrombocytopenia

A
  1. Failure of platelet production by megakaryocytes
  2. Shortened half life of platelets
  3. Increased pooling of platelets in an enlarged spleen
    (hypersplenism) + shortened half life
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7
Q

what are the hereditary platelet defects?

A

Glanzmann’s thrombasthenia = absent glycoprotein 2b/3a
Bernard Soulier syndrome lack of glycoprotein 1b
Storage Pool disease problem with storage granules

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8
Q

what issues can occur with VWF?

A

Von Willebrand disease
Hereditary decrease of quantity +/ function (common)
Acquired due to antibody (rare)

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9
Q

what are the functions of VWF in haemostasis?

A

-Binding to collagen and capturing platelets

-Stabilising Factor VIII
Factor VIII may be low if VWF is very low

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10
Q

how is VWD acquired?

A

VWD is usually hereditary
Deficiency of VWF (Type 1 or 3)
VWF with abnormal function (Type 2)

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11
Q

what issues can occur with the vessel wall?

A

Inherited (rare) Hereditary haemorrhagic telangiectasia Ehlers-Danlos syndrome and other connective tissue disorders

Acquired: Scurvy, Steroid therapy, Ageing (senile purpura), Vasculitis

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12
Q

disorders of primary haemostasis summarised:

A

Platelets
Thrombocytopenia
Drugs

Von Willebrand Factor
Von Willebrand disease

The vessel wall
Hereditary vascular disorders
Scurvy, steroids, age

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13
Q

what is bleeding like in disorders of primary haemostasis?

  • typical primary haemostasis bleeding
  • thrombocytopenia
  • severe VWD
A 
Typical primary haemostasis bleeding:
Immediate 
Prolonged bleeding from cuts
Epistaxes
Gum bleeding
Menorrhagia 
Easy bruising
Prolonged bleeding after trauma or surgery

Thrombocytopenia – Petechiae
Severe VWD – haemophilia-like bleeding

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14
Q

what are the tests for disorders of primary

A

Platelet count, platelet morphology
Bleeding time (PFA100 in lab)
Assays of von Willebrand Factor
Clinical observation

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15
Q

summarise blood coagulation

A
  1. Biological amplification system in which proteins are activated sequentially
  2. Incredibly efficient: 1 mole XIa generates ~107 moles thrombin
  3. Clotting factors numbered I - XIII
    I Fibrinogen
    II Prothrombin
    III Tissue Factor
    IV Calcium ions
    VI Activated factor V (Va)
  4. Factors II, VII, IX & X require a post-translational vitamin K dependent modification
  5. Most clotting factors (except V, VIII and XIII) are serine proteases
  6. Factors V & VIII are co-factors/Factor XIII is a transglutamidase
  7. Phospholipid derived from activated platelet membrane
    Fibrin mesh binds and stabilises platelet plug and other cells
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16
Q

what s the bleeding pattern like for disorders of coagulation?

A

The role of the coagulation cascade is to generate a burst of thrombin which will convert fibrinogen to fibrin

Deficiency of any coagulation factor results in a failure of thrombin generation and hence fibrin formation

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17
Q

what is required for a clotting in a larger vessel?

A

The primary platelet plug is sufficient for small vessel injury
In larger vessels it will fall apart
Fibrin formation stabilises the platelet plug

18
Q

what is haemophilia?

A

failure to generate fibrin to stabilise platelet plug

19
Q

what are the disorders of coagulation?

A

*Deficiency of coagulation factor production
-Hereditary
Factor VIII/IX: haemophilia A/B
-Acquired
Liver disease
Dilution
Anticoagulant drugs – warfarin

*Increased consumption
Acquired
Disseminated intravascular coagulation (DIC)
Immune - autoantibodies

20
Q

what are the differences between these coagulation factor deficiencies?

A

Factor VIII and IX (Haemophilia)
Severe but compatible with life
Spontaneous joint and muscle bleeding

Prothrombin (Factor II)
Lethal

Factor XI
Bleed after trauma but not spontaneously

Factor XII
No excess bleeding at all

21
Q

what can acquired coagulation disorders be due to-more common in hospital practice

A

Liver failure – decreased production
Most coagulation factors are synthesised in the liver

Dilution
Red cell transfusions no longer contain plasma
Major transfusions require plasma as well as rbc and platelets

22
Q

how can increases consumption leads to acquired coagulation disorders?

A

Disseminated intravascular coagulation
increased consumption

Generalised activation of coagulation – Tissue factor
Associated with sepsis, major tissue damage, inflammation
Consumes and depletes coagulation factors
Platelets consumed
Activation of fibrinolysis depletes fibrinogen
Deposition of fibrin in vessels causes organ failure

23
Q

what is bleeding like in coagulation disorders

A

superficial cuts do not bleed (platelets)
bruising is common, nosebleeds are rare
spontaneous bleeding is deep, into muscles
and joints
bleeding after trauma may be delayed and is prolonged
frequently restarts after stopping

24
Q

what’s a hallmark for haemophilia?

A

haemarthrosis

25
Q

what are the clinical distinctions between bleeding due to platelet and coagulation defects?

A 
-Platelet/Vascular
Superficial bleeding 
into skin, mucosal 
membranes
Bleeding immediate
after injury
-Coagulation
Bleeding into deep
tissues, muscles,
joints
Delayed, but severe
bleeding after
injury. Bleeding
often prolonged
26
Q

what are the tests for coagulation disorders?

A

Screening tests (‘clotting screen’)
Prothrombin time (PT)
Activated partial thromboplastin time (APTT)
Full blood count (platelets)

Factor assays (for Factor VIII etc)
Tests for inhibitors
27
Q

which pathways are APTT and PT used for?

A

APTT used for the intrinsic pathway (12,11,8,9)

PT used for the extrinsic pathway (7,5,10,2 and TF)

28
Q

what is the APTT for those with haemophilia?

A

prolonged APTT because there is no factor 8

29
Q

what bleeding disorders are not detected by routine clotting tests?

A 
Mild factor deficiencies
 von Willebrand disease
 Factor XIII deficiency (cross linking)
 Platelet disorders
 Excessive fibrinolysis
 Vessel wall disorders
 Metabolic disorders (e.g. uraemia)
 (Thrombotic disorders)
30
Q

what are the disorders of fibrinolysis?

A

Disorders of fibrinolysis can cause abnormal bleeding but are rare
Hereditary
antiplasmin deficiency

Acquired
drugs such as tPA
Disseminated intravascular coagulation

31
Q

what is the hereditary pattern with haemophilia?

A

sex linked recessive

32
Q

what is the hereditary pattern like with VWD?

A

autosomal disorder

Type 2, (Type 1) AD
Type 3 AR

33
Q

what is the hereditary pattern like with the rest(V, X etc.)?

A 
Autosomal recessive (AR) 
And therefore much less common
34
Q 
treatment of abnormal haemostasis: 
what do you do when the following occurs? 
-failure of production/function
-immune destruction
-increased consumption
A 
Failure of production/function
Replace missing factor/platelets
Prophylactic
Therapeutic
Stop drugs

Immune destruction
Immunosuppression (eg prednisolone)
Splenectomy for ITP

Increased consumption
Treat cause
Replace as necessary

35
Q

what are the three types of factor replacement therapy and what do they contain?

A

-Plasma
Contains all coagulation factors

-Cryoprecipitate
Rich in Fibrinogen, FVIII, VWF, Factor XIII

-Factor concentrates
Concentrates available for all factors except factor V.
Prothrombin complex concentrates (PCCs) Factors II, VII, IX, X

-Recombinant forms of FVIII and FIX are available.

36
Q

what is gene therapy for?

A

haemophilia B (or A)

37
Q

difference between haemophilia A and B

A

A factor 8

B factor 9

38
Q

what is platelet replacement therapy

A

Pooled platelet concentrates available

39
Q

what are the additional haemostatic treatments?

A

DDAVP
Tranexamic acid
Fibrin glue/spray

40
Q

what is desmopressin?

A

Vasopressin derivative

2-5 fold rise in VWF-VIII (VIII>vWF)

Releases endogenous stores -
Hence only useful in mild disorders

41
Q

what does tranexamic acid do?

A

Inhibits fibrinolysis
Widely distributed – crosses placenta
Low concentration in breast milk

42
Q

what is APTT?

A

The aPTT is one of several blood coagulation tests. It measures how long it takes your blood to form a clot. Normally, when one of your blood vessels is damaged, proteins in your blood called clotting factors come together in a certain order to form blood clots and quickly stop bleeding.

Year 2 haem mine (11 decks)

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